The Skeleton cave is located within the Vale, at the cords 170, 062.
This cave is home to a few different skeletons
Black Skeleton (Black in color) 170,000xp Dark amber
Skeleton Je (Green in color) 200,000xp Yellow amber, (RARE: Bone)
Skeleton Ja (Dark Brown in color) 240,000xp Dark Amber
Skeleton Ji (light brown in color) 280,000 Bone
Skeleton Sa (Light brown wielding a sword) 2,500,000xp drops no items